The present invention relates to a novel grain boundary-free crystalline body of a manganese-based composite oxide and a method for the preparation thereof as well as to a switching-type magnetoresistance device by the use thereof.
Pursuant to the discovery of high-temperature super-conductivity in copper oxides reported in recent years, the spin charge-coupled property of transition metal oxides has acquired renewed interests of investigators leading to the intensive investigations undertaken world-wide concerning manganese oxide-based materials having a perovskite-type crystalline structure and capable of exhibiting the phenomenon of giant magnetoresistance.
One of the manganese oxide-based materials of the perovskite structure exhibiting the negative giant magneto-resistance known heretofore is an epitaxial thin film having a chemical composition of La.sub.0.67 Ca.sub.0.33 MnO.sub.x epitaxially grown on a substrate of lanthanum aluminate LaAlO.sub.3 reported in Science, volume 264 (1994), pages 414-415. However, no prior art literatures are available relating to a single crystalline body or grain boundary-free crystalline body of such a composition.
On the other hand, crystalline ceramics based on a manganese oxide having a perovskite structure are known although each of them heretofore reported is an agglomerate body consisting of a great number of minute crystals demarcated by a large number of grain boundaries. Namely, no single crystalline body of this type is also known.